Soft robotic actuators utilizing asymmetric surfaces

ABSTRACT

A soft robotic actuator is disclosed. The actuator includes a first portion with a substantially constant profile and a second portion with a regularly varying profile, and bends in a pressure-dependent fashion as the internal pressure within the actuator is increased or decreased.

RELATED APPLICATIONS

The present application is a Continuation of U.S. patent applicationSer. No. 14/734,719 filed on Jun. 9, 2015, which claims priority to U.S.Patent Application No. 62/009,659, filed on Jun. 9, 2014. The contentsof the aforementioned application are incorporated herein by reference.

This application is a Continuation of related to International PatentApplication Publication No. WO2012/148472 by Ilievsky et al. The entiredisclosure of this reference, and any other reference listed in the bodyof this specification, is hereby incorporated by reference in itsentirety for all purposes.

FIELD OF THE DISCLOSURE

The disclosure relates generally to flexible actuators, and moreparticularly to soft robotic manipulators.

BACKGROUND

A “robot” is an automatically controlled, programmable, multipurposemanipulator which can function at a fixed location, or in motion.Robotics is a field of enormous (and growing) importance, in fields fromassembly to surgery. Most robotic systems are “hard”, that is, composedof metallic structures with joints based on conventional bearings. Thesestructures are often modeled after animal limbs (although structures notfound in nature—for example, wheels and treads—are also common in mobilerobots).

In an effort to build robots that can carry out sophisticated tasks inunstructured environments, researchers continue to emulate livingcreatures and their materials, morphology and movements. Over the lastseveral years, soft robotic manipulators have generated significantinterest due to their wide range of potential applications that arechallenging for “hard” robots. For example, soft robots can handledelicate objects such as eggs because the surface of soft robots canconform to the shape of the handled objects. Soft robots can also fitinto places that are challenging for hard robots. For instance, a softrobot can fit under a door jam by deflating itself. In addition, softrobots can move in an environment that are challenging for hard robots.For instance, soft robots can maneuver on non-stiff surfaces, such asmud, clay, gel, or in fluids such as water.

One way to build a soft robotic manipulator is by integrating rigidrobotic skeletons with soft skins or compartments. However, thesestructures can only move in limited ways. In addition, rigid skeletonsmay not be suited for many applications, such as manipulating delicateobjects or objects with significant part-to-part variance.

Pneumatic artificial muscles, such as McKibben actuators, arecontractile or extensional devices operated by pressurized air.McKibben-type actuators have a simple structure consisting of aninternal bladder wrapped in a braided mesh shell. The braided mesh shellincludes flexible yet non-extensible threads oriented at a bias aroundthe bladder. When the internal bladder is pressurized, the pressurizedair pushes against the inner bladder surface and external shell, causingthe bladder to expand. Like the Chinese finger puzzle, the braided meshshell shortens in a scissor-like action due to the non-extensibility ofthe threads. As the braided mesh shell shortens, the actuator shortensaccordingly, thereby exerting a force in the direction of contraction.These actuators can be fast and can have length-load dependence similarto that of muscles, but possess only one mode of actuation—contractionand extension.

Soft robots, or soft robotic actuators, can be most easily identified bythe materials used in their manufacture and their methods of actuation.The field of soft robotic actuation began with work by Kuhn et al in1950. Kuhn et al focused on the reversible change of a polymericmaterial, namely the coiling and uncoiling. The reversible change of apolymeric material depends on the acidity of the surrounding medium.Kuhn et al leveraged this property to successfully move a weight. Thisdemonstrated the possibility of using soft materials in roboticactuation. Hamlen et al extended this idea in 1965 and showed thatpolymeric materials can be contracted electrolytically.

Kuhn et al and Hamlen et al set the scene for using the polymeric gelsfor soft robotics. In particular, Otake et al demonstrated the use ofelectro-active polymers in the manufacture of starfish-shaped roboticactuators. Also, in 1996, Suzumori et al demonstratedpneumatically-driven soft actuators. These actuators were configured torespond to pressurization of sealed chambers fabricated from extensiblepolymers. This type of actuation has been used on the millimeter scaleto fabricate grippers, tentacles, and other related devices includingpneumatic balloon actuators.

As the field has progressed, there has been an ongoing need to developcompliant actuators with actuation dynamics adapted to the growing listof applications for soft robotic devices. There is also a need in thefield for design frameworks for the development of new actuators basedon quantitative modeling and the manipulation of a relatively smallnumber of actuator parameters.

SUMMARY

The present invention addresses the needs described above by providingactuators that are configured to perform new fundamental motions throughthe inclusion of design elements which can be configured, through themanipulation of a relatively short list of parameters, to undergospecific pressure-actuated changes which can be designed usingquantitative modeling techniques.

In one aspect, the present invention relates to a soft robotic actuatorthat includes a flexible or elastic elongate body that defines a sealedvoid which can be pressurized or depressurized relative to theenvironment surrounding the actuator. The elongate body includes a firstwall portion with a substantially uniform shape or profile and, oppositethe first wall portion, a second wall portion with a repeating variablewall portion. The internal height of the elongate body varies over itslength. Pressurizing or depressurizing the flexible or elastic elongatebody causes at least a part of the flexible or elastic elongate body,and thus the actuator, to bend. The profile of the second wall portionis characterized by a maximal wall height, a minimal wall height, and apitch (measured as the peak-to-peak distance between adjacent repeatingsegments, each of which is capable of undergoing actuation in responseto internal pressurization, or “unit cells”). Each of these parameters,as well as the wall thickness of the elongate body, can be varied to“tune” the actuator's pressure sensitivity, i.e. to cause the actuatorto curve at a pre-determined rate in response to changes in the internalpressure of the flexible or elastic elongate body. In some cases, theflexible or elastic elongate body defines a lumen extending between theproximal and distal ends of the elongate body, which lumen ispermanently or reversibly (e.g. by means of a valve) open to theexterior of the device at the distal end. The lumen can be connected,variously, to a source of pressure (including negative pressure), asource of fluid, or a medical device that includes an elongate portionwhich is capable of being inserted into and passed or extended throughthe lumen to reach the exterior of the device. The distal opening of thelumen can include a suction cup, and the flexible or elastic elongatebody can generally incorporate useful tools such as cutting implements(e.g. blades, scalpels, etc.), hooks, and needles at its distal end. Insome cases the soft robotic actuator includes a chamber containing agranular material that is normally pliant but which becomes rigid whenair is evacuated from the chamber by the application of a vacuum.

In another aspect, the present invention relates to a soft roboticactuator which includes two or more (i.e. a plurality of) flexibleelongate bodies as described above. The elongate bodies are optionallyplaced in a parallel arrangement in which their first wall portions areproximate one another and face inward, while their second wall portionsface outward.

In another aspect, the present invention relates to a medical devicethat includes two or more (i.e. a plurality of) soft robotic actuatorsarranged to define a grasping member (i.e. a device which can grasp andrelease an object). Each actuator includes one or more flexible elongatebodies as described above.

In still another aspect, the present invention relates to a medicaldevice that includes an elongate element and a plurality of soft roboticactuators as described above. The elongate element defines one or morelumens connected to the voids within each actuator. In variousembodiments, the device includes an enclosing element that is removablyor reversibly disposed about the actuators to reduce mechanicalinterference with the body during insertion of the device. In somecases, the device includes two actuators connected to the distal end ofthe elongate member via a “Y” joint. A spring for urging the actuatorsapart may be disposed at the Y joint in some cases.

In still another aspect, the present invention relates to the use of adevice according to an embodiment of the invention to treat a patient byinserting it into the body of the patient and actuating an actuator tograsp a portion of the patient's body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A-D include a photograph and three schematic views of an exemplarysoft robotic actuator.

FIG. 2A-D show four separate schematic views of an exemplary softrobotic actuator.

FIG. 3A-C illustrate the pressure-sensitive bending of a soft roboticactuator according to some embodiments of the present invention.

FIG. 4A-E illustrate how varying certain physical parameters ofactuators according to the present invention alters their pressuresensitivity (i.e. the degree to which they curve in response to changesin internal pressure).

FIG. 5A-B illustrate certain physical dimensions of an actuatoraccording to an embodiment of the invention.

FIG. 6A-B are a schematic view of an actuator according to the presentinvention bending in response to the application of an internal vacuum.

FIG. 7A-B are a schematic view of an actuator incorporating a rigidizinggranular material according to certain embodiments of the presentinvention.

FIG. 8 is a schematic view of an actuator incorporating a workingchannel according to certain embodiments of the present invention.

FIG. 9A-E show various schematic views of actuators incorporatingsurgical instruments, suction cups, or other manipulators according tosome embodiments of the present invention.

FIG. 10 shows a schematic view of an actuator of the present inventionwhich incorporates a wire.

FIG. 11 shows a schematic view of an actuator of the present inventionwhich incorporates one or more vibration-damping materials.

FIG. 12 shows a multidirectional soft robotic actuator according to anembodiment of the present invention.

FIG. 13A-B show photos of a grasper that incorporates soft roboticactuators according to another embodiment of the present invention.

FIG. 14A-B show a complex actuator according to an embodiment of thepresent invention.

FIG. 15A-F show an exemplary surgical instrument according to anembodiment of the invention.

FIG. 16A-C show a portion of a surgical instrument according to anembodiment of the invention packaged for deployment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. The invention, however, may be embodied inmany different forms and should not be construed as being limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. In thedrawings, like numbers refer to like elements throughout.

In accordance with the present disclosure, a compact, portable, “softrobotic” actuator which bends or otherwise alters its profile uponchanges in curvature induced by extension of programmed unfolding andstraining regions of the actuator is provided. Actuators according tovarious embodiments of the invention utilize a kinematically motivatedratio of arc lengths between opposing faces on the actuator. These arclength ratios are selected so that the actuator unfolds or folds to apredetermined final profile. The final profile may include any shape orcombination of shapes that are useful for a particular application. Forinstance, the final profile may bend, twist, extend, and/or contract theactuator.

Actuators according to the invention, as described more fully herein,have several advantages relative to existing actuator designs: first,actuators according to the invention generally (though not necessarily)have linear actuation profiles, meaning that they undergo a fixeddisplacement (e.g. a reduction or increase in the radius of curvature,or a linear displacement of a distal end of the actuator relative to theproximal end). Second, actuators according to the present inventiongenerally have a broad and highly tunable dynamic range, which is animprovement over the more stepwise action of many currently usedactuators in which the actuation occurs over a small range above athreshold. Values below this threshold are essentially a dead-zone forpurposes of controlling the actuators. Third, actuators designedaccording to the principles of the present invention undergosignificantly less (e.g. four-fold or five-fold less) strain thanexisting actuator designs, reducing the likelihood of failure overmultiple actuation cycles and improving the reproducibility of actuationbetween cycles. Fourth, the present invention includes a framework fordesigning actuators in which relatively few parameters can be varied totune actuation profiles, simplifying the design and modeling ofactuators for specific applications, which reduces the need for physicalprototyping of actuator designs, shortening their time to deployment.

The resistance of the actuator to changes in curvature is determined bystrain induced in the materials from which the body is constructed. Suchresistance can be programmed within an extremely wide range ofmagnitudes, and may be modulated through the selection of specializedelastomeric or non-elastomeric materials and body geometries. In thisway, the resistance of the actuator to changing curvature may have acontrolled functional relationship to applied pressure or vacuum(linear, exponential, logarithmic, sinusoidal, etc.) and this functionalrelationship may be intentionally varied at different locations withinthe actuator. As an example, in some embodiments of the invention, aperiodic “accordion” shaped face is used opposing a flat face to providethe proper relative arc lengths for uniform bending and ensure thatstrain response is linear with respect to bending curvature. This can beviewed as similar to the mechanics of an extending or compressinghelical spring.

The functionality of this actuator can be enhanced by incorporation ofadditional features such as a jamming chamber to rigidize the actuatoron command, suction cups along the surface of the actuator to enhancegripping, and inclusion of nitinol wire or mesh to provide a combinationof fluid and electromechanical actuation.

Actuators and design features discussed herein are, in variousembodiments of the invention, integrated into a variety of actuatingstructures, including without limitation multi-chambered tentacles,multi-fingered grippers, surgical retractors, minimally invasivesurgical devices, and a multitude of other soft robotic assemblies.

Referring to FIG. 1, an exemplary soft actuator 100 according to certainembodiments of the invention includes opposing folding 110 andnon-folding 120 portions. FIG. 1A is a photograph of the soft actuator,while FIGS. 1B-D show various schematic views of the actuator 100,including a cross section FIG. 1D illustrating the spatial relationshipbetween folding 110 and non-folding 120 portions.

Turning to FIGS. 2A-B, soft actuators 100 according to the inventiongenerally include one or more unit cells 130, each cell 130 in turnincluding a single folded portion 110 on the opposing side of anactuator from a non-folded portion 120. A linear pattern of repeating,identical unit cells 130 can be combined to create a bending actuator100 with a constant radius of curvature, as shown in FIGS. 2C-D. As FIG.2 shows, as the internal pressure of the actuator 100 is increased, theactuator 100 curves around its non-folding portion 120. In thisarrangement, the relative length of the folding portion 110 increasesrelative to that of the non-folding portion 120 as the internal pressureof the actuator 100 increases.

In some cases, a complex bending motion can be programmed in to thestructure of a soft actuator by combining a set of unit cells ofdifferent height, pitch, and wall thickness in a linear pattern togenerate a bending actuator with a variable radius of curvature. Byconstructing a soft actuator with folds on multiple faces of theactuator it is possible to create a structure that generates multidirectional bending (e.g. a helical or serpentine shape) and/or twistingupon pressurization or application of vacuum.

Turning now to FIG. 3A-C, the degree of actuation of actuators accordingto embodiments of the invention can depend linearly, or non-linearly, onthe internal pressure applied to the actuator. FIG. 3A shows an actuator100 at rest, in which the internal pressure of the actuator is equal tothe external pressure (0 PSI) and the angular displacement between theproximal end 150 and the distal end 160 of the actuator is substantiallyzero (referred to as the degree of actuation for purposes of thisdisclosure). As the internal pressure within the actuator 100 increases,the angular displacement increases in a substantially linear fashionfrom between 0 and 90 degrees.

The relationship between the internal pressure of the actuator 100 andthe degree of actuation is determined at least in part by the geometryof the folding portion 110. FIG. 4A shows the relationships betweeninternal pressure and actuation where the various folding portions 110are characterized by (i) different maximal wall heights 111 as measuredfrom the internal surface of the non-folding portion 120 (ii) differentpitch distances, as measured from peak-to peak within a unit cell 130,and (iii) different wall thicknesses. In general, increasing the heighttends to increase the pressure sensitivity of the actuator 100, whileincreasing the wall thickness and the pitch tend to decrease itspressure sensitivity. Advantageously, the actuation profiles ofactuators according to various embodiments of the invention aregenerally linear over a broad range of pressures up to 15 PSI in somecases, and are responsive to pressures at a thresholds near zero PSI. Bycontrast, existing actuator designs are generally characterized byshorter dynamic ranges of, for instance, 3 or 4 PSI, and often timeshave higher pressure response thresholds than those observed in FIG. 4.As a consequence, existing actuator designs are generally lesscontrollable, as they have larger control “dead zones” and go from zeroactuation to full actuation over a relatively narrow pressure range,necessitating relatively fine control of applied pressures in order toachieve control over the degree of actuation.

Another advantage of actuator designs according to the present inventionis their minimization of strain caused by actuation through theincorporation of alternating “long” and “short” wall segments within thefolding regions 110, as shown in FIG. 5. In actuators according tovarious embodiments of the present invention, expansion of the foldingregion 110 is driven in part by the unfolding of these structures ratherthan solely by elongation due to strain as in existing actuator designs.The minimization of strain in actuators of the present inventiongenerally improves the consistency (i.e. the reproducibility) of theactuation path across multiple cycles, and reduces the risk ofmechanical failure due to material fatigue after multiple actuationcycles. By contrast, conventional actuator designs, in which actuationis generally accompanied by substantially greater strain, are more proneto hysteresis and may be more prone to failure after repeated cycles.

While the foregoing examples have focused on actuation driven byincreasing internal pressure within the actuator, in preferredembodiments, actuator 100 is also able to actuate in reverse in responseto decreased internal pressure, as shown in FIG. 6A-B. As the internalpressure within the actuator 100 is decreased, the relative length ofthe folding portion 110 decreases relative to that of the non-foldingportion 120 as the width of each unit cell 130 decreases and the wallsof the folding portion 110 are drawn together, thereby decreasing theradius of curvature of the actuator 100. This feature advantageouslypermits actuators of the invention to act in multiple directions asneeded for various applications.

In some embodiments, such as the one shown in FIG. 7A-B, the actuator100 includes a cavity 170 which contains a granular material 171 that issoft and/or pliant at ambient pressures, but which becomes rigid uponapplication of vacuum via vacuum jamming. In a preferred embodiment ofthe invention, cavity 110 is defined by and/or part of the non-foldingportion 120 of the actuator 100. In use, the actuator 100 is firstpressurized or depressurized to induce a desired curvature within theactuator 100. A vacuum is then applied to the cavity 170, causing thegranular material 171 to rigidize and hold its shape. This arrangementpermits the actuator 100 to hold its bent shape even as the pressurewithin the actuator 100 returns to ambient pressure.

In certain embodiments, such as the one shown in FIG. 8A-B, actuators100 of the invention define one or more working channels 180, which isopen to an exterior of the actuator 100 and which extends through atleast part of the length 100 of the actuator 100 to permit theintroduction or evacuation of materials through the actuator 100. Invarious embodiments, working channels 180 are used to provide irrigationor suction at a point near the distal end 160 of the actuator 100, orare used to permit the use of spectroscopic, imaging, fiber-opticillumination, electrodes, laser sources, ultrasound probes, etc. throughthe actuator 100. While the examples set forth in this specificationfocus on working channels that define a single lumen extending from theproximal end of the actuator to the distal end, it will be understood bythose of skill in the art that any number of lumens, and any number ofproximal or distal openings, may be used, depending on the specificapplication for which the actuator is to be used. For instance, anactuator may include a working channel with multiple exit points nearthe distal end of the actuator for purposes of providing irrigation.

In addition to, or in lieu of, a working channel 180, actuators canincorporate other features that facilitate manipulation or intervention.These features are generally, but not necessarily, positioned at thedistal end 160 of the actuator 100 and/or adjacent to the workingchannel 180. FIG. 9A, for instance, shows a cross section of an actuator100 which includes a suction cup 181 disposed at the end of the workingchannel 180 to permit the distal end 160 of the actuator 100 to gripobjects via the application of negative pressure through the workingchannel 180. FIG. 9B-E shows other tools 190 that are placed on thedistal portion 160 of the actuator in various embodiments, including ahook 191, a cutting instrument such as a knife 192, a needle 193, etc.

Actuator 100 includes one or more wires for the delivery of monopolarand/or bipolar current for electrosurgery, and/or to provide current andpotential for embedded devices such as sensors. Any sensor whichmeasures a variable of interest can be used with an actuator accordingto the invention. Variables that can be measured by such sensorsinclude, without limitation, temperature, conductivity, pH, oxygen,pressure, or the concentration of one or more of glucose, creatinine,urea, carbon dioxide, hemoglobin, microbe or virus counts, etc.). Thewire or set of wires can be incorporated into a wall of the actuator 100(e.g. the wall of the non-folding portion 120), located in a workingchannel 160, or run through the interior of the actuator 100. In caseswhere the wire or set of wires are embedded in wall of the non-foldingportion 120, the wire(s) can be straight or can be have a shape thataccommodates the extension, retraction, and/or curvature of the actuator100, for example coiled, zigzag, sinusoid, grid, meshes, etc.

In some embodiments, as shown in FIG. 11, a damping material 101, suchas a silicone or urethane foam, is incorporated into the body of theactuator 100, or is otherwise attached to the actuator 100 to dampenoscillation of the actuator during and/or after actuation or aftercontact with another object. The quantity of the material, and themechanical properties thereof, are generally chosen to achieve a desiredlevel of damping without increasing the resistance to actuation to anundesirable degree

Actuators according to the device can be combined to form larger-scaleactuatable structures, such as the multi-directional actuator 200 shownin FIG. 12. As an example, the figure shows three actuators 205, 210,215, each including a folding portion and a non-folding portion asdescribed above. The actuators are positioned in a more-or-lesstriangular or circular arrangement, when viewed from the top, in whichthe non-folding portions of each of the actuators 205, 210, 215 areclosely apposed and inward facing while the folding portions face out.By pressurizing or depressurizing a single actuator, themulti-directional actuator 200 undergoes a simple displacement insubstantially one direction. However, by pressurizing or depressurizingtwo or more of the actuators 205, 210, 215 in tandem, complex movementsand/or applications of force are made possible. In the example presentedabove and in FIG. 12, the actuators are identical, and are arranged soas to oppose one another, at least in part. It will be appreciated byskilled artisans, however, that the actuators used in assemblies of theinvention may be different, and need not necessarily be arranged inopposition to one another, depending on the type of actuation desired.

Multiple actuators can also be combined to form grasping elements, asshown in FIG. 13A-B. The grasping element 300 as shown incorporatesthree separate actuators 305, 310, 315, though in other embodiments, anysuitable number of actuators can be used, including two, three, four,five, six, etc. The actuators are arranged in a substantially triangularor circular fashion, such that their respective distal ends 306, 311,316 define an area which decreases as the actuators are actuated (eitherby pressurization or depressurization, depending on the orientation ofthe actuators), thereby allowing the grasping element 300 to “grasp” anobject using the actuators 305, 310, 315 as “fingers.”

The principles of the invention can be used to generate individualactuators which are capable of complex actuating movements, as shown inFIG. 14A-B. An exemplary actuator 400 according to one embodiment,incorporates two groups of unit cells, denoted A and B in the figure,with different heights, pitches, or wall thicknesses. These two groupsof unit cells exhibit different pressure sensitivities, and formseparate segments which bend at different rates. In the example shown inFIG. 14, each unit B has a lower height than an adjacent unit A, sothat, as the actuator is pressurized, its actuation is similar to theaction of a finger in that the B segments act as joints while the Asegments remain straight.

FIGS. 15 and 16 depict a surgical instrument 500 which utilizes aplurality of “finger” actuators according to the invention. Theinstrument 500 includes an elongate element 510 that has a distalportion insertable into a patient. The elongate element 510 ispreferably a catheter, cannula, or other structure having sufficientcolumn strength to permit insertion within a body and having at leastone lumen (not pictured) for supplying pneumatic or hydraulic actuationto a plurality of actuators 520, 530, disposed at a distal end of theelongate element 510. (In preferred embodiments, the elongate element510 includes a separate lumen for each actuator, thereby enabling theindependent actuation of each actuator.) The actuators 520, 530 arepreferably shaped to form a “Y” joint with the distal portion of theelongate element 510, and optionally include a spring element 540disposed at or near the Y joint for urging the actuators 520, 530 apartat their proximal ends. The actuators can incorporate any of thestructural features discussed above, and are variously uniform(comprised of identical unit cells) or varied, for instance toincorporate a “joint” comprising one or more unit cells with a higherpressure sensitivity than the other unit cells making up the actuator.At its proximal end, the elongate element 510 is connectable to apressure source (not pictured) and optionally includes a connector asknown in the art, such as a threaded male or female luer connector.

To facilitate insertion of the distal portion of the surgical instrument500, including the actuators 520, 530, into the body of a patient, andshield them from undesirable mechanical interference, the instrument 500optionally includes one or more enclosing elements 550. FIG. 15 depictsone embodiment in which the enclosing means is a capsule 551, which canat least partially envelop the actuators 520, 530 during insertion ofthe instrument 500 into the body of a patient. The capsule 551 isremovable in some embodiments, either via mechanical means such as ahinge or spring, or through dissolution or erosion. In otherembodiments, such as the one shown in FIG. 15, the capsule isretractable and is capable of being closed after it has been retractedto expose the actuators 520, 530. In still other embodiments, theactuators 520, 530 are initially contained within a retractable sheath(not pictured), which can be withdrawn over the actuators 520, 530 todeploy them.

In use, the distal end of an instrument 500 according to the inventionis placed into the body of a patient using any suitable pathway,including without limitation percutaneously (e.g. through a trocar 560),endoscopically or laparoscopically. Once in place, the enclosing element550 is withdrawn, opened, or otherwise manipulated to expose theactuators 520, 530 at the distal end of the instrument prior to its usein a medical procedure. Instruments according to the invention areparticularly well suited for the manipulation of soft tissues such asbowel tissue, or for use in constrained spaces where rigid instrumentscould pinch, impinge or otherwise apply undesirable force to tissues andorgans adjacent a surgical site of interest.

The actuators 520, 530 are, optionally, able to be collapsed into aspace-saving configuration for insertion into the body. For instance, asshown in FIG. 16, the folding portions of the actuators 520, 530 may beinterdigitated prior to and during delivery to reduce their profile andease insertion into the body. A removable clip 570 may also be used toconstrain the actuators 520, 530 during insertion.

For the sake of simplicity, the examples presented above have focused onembodiments incorporating folding and non-folding portions, but certainactuators according to the embodiments of the invention incorporatefirst and second extensible portions with varying pressureresponsiveness in opposition to one another. The use of two first andsecond folding portions in opposition to one another can, for instance,give rise to both extension and bending. In addition, the embodimentsabove have generally focused on linear arrangements of the folding andnon-folding portions, but non-linear arrangements can be used as well togive rise to complex actuation movements. For instance, an elongateactuator in which the folding and non-folding portions form a spiralarrangement will actuate to form a helical structure.

In addition, the foregoing examples have focused on folding portionswith more-or-less sinusoidal geometries, but it should be appreciatedthat any geometry which incorporates alternating “peaks” and “valleys”may be suitable for use with various embodiments of the invention.

Finally, this specification has focused on actuators that incorporate“flexible elongate bodies,” but it will be appreciated by those of skillin the art that actuators optionally or preferably, depending on theapplication, comprise materials that are not only flexible (capable ofbending or otherwise deforming under the application of a force) butelastic (capable of bending or deforming under a force and returning toits original shape upon withdrawal of the force), stretchable orelastomeric.

As used herein, an element or step recited in the singular and proceededwith the word “a” or “an” should be understood as not excluding pluralelements or steps, unless such exclusion is explicitly recited.Furthermore, references to “one embodiment” of the present invention arenot intended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features.

While the present invention has been disclosed with reference to certainembodiments, numerous modifications, alterations and changes to thedescribed embodiments are possible without departing from the sphere andscope of the present invention, as defined in the appended claim(s).Accordingly, it is intended that the present invention not be limited tothe described embodiments, but that it has the full scope defined by thelanguage of the following claims, and equivalents thereof.

The invention claimed is:
 1. A soft robotic actuator, comprising: anelongate body having a first wall portion having a first profile and asecond wall portion disposed opposite the first wall portion, the secondwall portion having a repeating variable profile such that a height ofthe elongate body varies over its length, wherein (a) the elongate bodydefines a sealed void which is capable of being pressurized relative tothe environment around the actuator, and (b) a distal end-of theelongate body is configured to exhibit angular displacement underpressurization, due at least in part to the repeating variable profileof the second wall portion, wherein the angular displacement increasesin direct proportion to the pressure applied from an ambient pressure toa pressure according to a final curve profile.
 2. The soft roboticactuator of claim 1, wherein a length of the second wall portionincreases relative to a length of the first wall portion when theportion of the elongate body is bent, wherein the portion of theelongate body is bent when the pressurizing causes a corresponding partof the second wall of the elongate body to unfold.
 3. The soft roboticactuator of claim 1, wherein the second wall portion comprises aplurality of unit cells, wherein each unit cell comprises a respectivemaximal wall height and a respective minimal wall height, wherein themaximal and minimal wall heights are relative to the first wall portionof the corresponding unit cell.
 4. The soft robotic actuator of claim 3,wherein the soft robotic actuator has a constant radius of curvaturewhen: (i) the maximal wall heights of each unit cell are substantiallyequal, and (ii) the minimal wall heights of each unit cell aresubstantially equal.
 5. The soft robotic actuator of claim 3, whereinthe soft robotic actuator has a variable radius of curvature when atleast one of: (i) the respective maximal wall heights of a first unitcell and a second unit cell, of the plurality of unit cells, aredifferent, (ii) a wall thickness of the first unit cell is differentthan a wall thickness of the second unit cell, and (iii) a pitchdistance between a first two adjacent unit cells of the plurality ofunit cells is different than a pitch distance between a second twoadjacent unit cells of the plurality of unit cells.
 6. The soft roboticactuator of claim 1, wherein the bend comprises one or more of: (i)multi-directional bending of the elongate body, and (ii) twisting of theelongate body, responsive to the pressurizing.
 7. The soft roboticactuator of claim 1, wherein a degree of actuation of the soft roboticactuator is based on an amount of pressure in the pressurized sealedvoid.
 8. The soft robotic actuator of claim 7, wherein the degree ofactuation is further based on one or more of: (i) the height of theelongate body, (ii) a respective pitch difference between two adjacentunit cells, of a plurality of unit cells of the second wall portion, and(iii) a respective wall thickness of each unit cell.
 9. The soft roboticactuator of claim 1, wherein the elongate body curves around the firstwall portion when bent.
 10. The soft robotic actuator of claim 1,wherein the elongate body comprises an elastic elongate body thatreturns to an original shape in the absence of pressurization in thesealed void.
 11. The soft robotic actuator of claim 1, furthercomprising a tapered distal end.
 12. A device, comprising: a pluralityof soft robotic actuators arranged to define a grasping member, eachsoft robotic actuator including a flexible elongate body, each elongatebody comprising a first wall portion having a substantially constantprofile and a second wall portion disposed opposite the first wallportion, the second wall portion having a repeating variable profilesuch that a height of the elongate body varies over its length, wherein(a) each elongate body defines a sealed void which is capable of beingpressurized relative to the environment around the correspondingactuator, and (b) each elongate body is configured to exhibit angulardisplacement of its distal end under pressurization, due at least inpart to the repeating variable profile of the second wall portion,wherein the angular displacement increases in direct proportion to thepressure applied from an ambient pressure to a pressure according to afinal curve profile.
 13. The device of claim 12, wherein the pluralityof actuators are arranged about a single longitudinal axis.
 14. Thedevice of claim 12, wherein a distal end of each actuator defines agrasping area which increases or decreases based on an amount ofpressure in the sealed void of each elongate body.
 15. The device ofclaim 12, wherein a length of the second wall portion of each actuatorincreases relative to a length of the first wall portion when therespective portion of the respective elongate body is bent, wherein arespective portion of the respective elongate body is bent when thepressurizing causes a corresponding part of the second wall of theelongate body to unfold.
 16. The device of claim 12, wherein the secondwall portion of each actuator comprises a plurality of unit cells,wherein each unit cell comprises a respective maximal wall height and arespective minimal wall height, wherein the maximal and minimal wallheights are relative to the first wall portion of the corresponding unitcell.
 17. A method of actuating a soft robotic actuator, the methodcomprising: providing a soft robotic actuator of claim 1; andpressurizing the soft robotic actuator to cause the second wall toexpand preferentially, thereby causing the soft robotic actuator to bendaround the first wall of the soft robotic actuator.
 18. The soft roboticactuator of claim 1, wherein the predetermined range of pressures atleast includes 1-5 PSI.
 19. The soft robotic actuator of claim 1,wherein the predetermined range of pressures is 0-15 PSI.